1. Field of the Invention
The present invention relates to an image displayer, and more particularly, to an image displayer having an afterimage-elimination function.
2. Description of the Related Art
Generally, displayers such as a Cathode Ray Tube (CRT), a Liquid Crystal Display (LCD), a Plasma Display Panel (PDP), and the like for displaying an image have a drawback that their fluorescent substance or light emitting device is deteriorated or deformed when a display of a still picture continues for a long time. For example, when an image displayer displays stock quotations, since a still picture having characters and graphs concentrated on specific pixels of the image displayer is displayed for a long time, it is often the case that the lifespan of the specific pixels become shorter than those of their neighboring pixels. In the case of a PDP, which uses ultraviolet rays generated during a gas discharging to display an image, the problem of deterioration of pixels becomes more serious. The PDP applies an electric field to a tube having helium and a xenon gas injected therein in order to generate light. Even though the supply of the electric field is stopped, the electric field still remains for a predetermined time, causing an electric discharge to occur. That is, the PDP displays the still picture including the characters and the graphs for the stock quotations program, with a result that the specific pixels corresponding to the still picture continues emitting the light and the specific pixels become brighter than required. Due to such remaining electric field, the pixels have an afterimage of the still picture which remains when the still picture is changed into another picture.
In order to minimize the afterimage, a variety of methods have been conventionally suggested. For example, one of them, as shown in FIG. 1, is to reduce the afterimage by moving a picture position up and down and right and left at regular time intervals when a still picture is displayed on a screen and/or a display beyond a predetermined time. According to this method, the time interval and the length of the movement of the picture position can be adjusted for the user's convenience. Accordingly, the picture as displayed returns to the original position after a predetermined time and the pixels of the still picture can be protected to some degree. However, the user feels inconvenience because the picture has to be moved when he/she is viewing the picture. Also, since the moving path is determined at each time interval, the pixel having the moving path as determined cannot be completely prevented from deteriorating and thus the afterimage cannot be prevented.
Another method has the aim of reducing a luminosity of each of the pixels consisting a still picture to 50%. However, this method cannot prevent the deterioration of the pixels and the afterimage occurring when the still picture is displayed for a long time.
Still another method is to convert a picture itself to a reverse picture in accordance with a user's selection of a menu as shown in FIG. 1B, and then return it to the original picture. In this case, if a user is not aware of the features of a product, it is difficult for the user to execute this method. Especially, in the case of an expensive PDP, the problem of the afterimage becomes more serious.